Not going to happen. The fan outrage would be too much, and Nintendo knows it (because they have the ballot results). Putting in a chance to get new characters and then giving everyone a repeat would burn too much good will.
If they had not already released Lucas, Roy, and Mewtwo, Wolf might be a believable ballot winner. But at this point, everyone would think Wolf was planned from the beginning and the ballot didn't matter, which would be terrible for PR.
Yes and no. This is almost certainly what will happen, but not in the way you expect.
The "Top 25" idea is ridiculous. Let's say that the top two each have a million votes, and the next twenty three all have a hundred apiece. "Oh, they're Top 25, we'll still look at them". Not going to happen. Position on the ballot will mean nothing next to number of votes total. If there are a couple of close runners up, Sakurai might choose them over K. Rool. But they'd have to be close in terms of number of votes, and there aren't many who can claim that status.
Even fewer once we start factoring in eligibility (aka: Shovel Knight won't get in because he's never been released in Japan).
Also not going to happen, as that was what they created the ballot for. Again, fan feedback. You don't create something like that, let fans believe it's for DLC, then cancel it. They will announce a DLC character as a ballot winner.